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Mi Chung Suh@m

 

Chonnam National University, Republic of Korea

Biosynthesis and export of cuticular wax in Arabidopsis thaliana

 

 

The aerial parts of all land plants are covered with cuticular waxes, which are synthesized by extensive export of intracellular lipids in epidermal cells to the surface, to limit non-stomatal water loss and gaseous exchanges. During the biosynthesis of cuticular wax, the C16 and C18 fatty acids synthesized in the plastids are further elongated to very-long-chain fatty acids (VLCFAs) by the fatty acid elongase complex on the ER. The generated VLCFAs are subsequently transformed into primary alcohols and wax esters by an acyl reduction pathway or aldehydes, alkanes, secondary alcohols and ketones by a decarbonylation pathway. Arabidopsis genome-wide microarray analysis of stems and stem epidermal peels provided putative candidate genes that might be involved in the biosynthesis and export of cuticular wax. Based on the microarray analysis, the 3-ketoacyl-CoA synthase 20 (KCS20), KCS2/DAISY, and KCS11 genes, which function in the condensation of C2 units to acyl-CoA during the fatty acid elongation process, were isolated. It was revealed that they have overlapping and non-redundant functions in the biosynthesis of cuticular waxes, suberin and sphingolipids, and are essential for cell division and elongation. In addition, cuticular wax layers are synthesized by the extensive export of intracellular lipids in epidermal cells. However, it is still not known how hydrophobic cuticular lipids can be exported into the plant surface through hydrophilic cell wall. Although it has been suggested that plant lipid transfer proteins (LTPs) are involved in cuticular lipid transport, the in planta evidence is still not clear. Based on the Arabidopsis genome-wide microarray analysis of the stem epidermal peels, glycosylphosphatidylinositol-anchored lipid transfer protein (LTPG1) and LTPG2 genes were also isolated and identified to be involved in cuticular wax export.

 

 

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[1] Jung JH, Kim HJ, Go YS, Lee SB, Kim JY, and Suh MC (2012) Arabidopsis 3-ketoacyl-CoA synthase 11 (KCS11), KCS2/DAISY, and KCS20 have overlapping and non-redundant functions in the biosynthesis of cuticular waxes, suberin, and sphingolipids and are essential for cell division and elongation. (Unpublished)

[2] Kim H, Lee SB, Kim HJ, Min MK, Hwang I, and Suh MC (2012) Characterization of glycosylphosphatidylinositol-anchored lipid transfer protein 2 (LTPG2) and overlapping function between LTPG/LTPG1 and LTPG2 in cuticular wax export or accumulation in Arabidopsis thaliana. Plant Cell Physiol. (Submitted)

[3] Lee SB, Jung SJ, Go YS, Kim HU, Kim J-K, Cho HJ, Park OK and Suh MC (2009) Two Arabidopsis 3-ketoacyl-CoA synthase genes, KCS20 and KCS2/DAISY, are functionally redundant in cuticular wax and root suberin biosynthesis, but differentially controlled by osmotic stress. The Plant J. 60: 462-475. Abstract

[4] Lee SB, Go YS, Bae H-J, Park JH, Cho SH, Cho HJ, Lee DS, Park OK, Hwang I and Suh MC (2009) Disruption of glycosylphosphatidylinositol-anchored lipid transfer protein gene altered cuticular lipid composition, increased plastoglobules and enhanced susceptibility to infection by the fungal pathogen, Alternaria brassicicola. Plant Physiol. 150:42-54. Abstract

[5] Suh MC, Samuels L, Jetter R, Kunst L, Pollard M, Ohlrogge J, Beisson F (2005) Cuticular lipid composition, surface structure, and gene expression in Arabidopsis stem epidermis. Plant Physiol. 139: 1-17. Abstract